Sound-damping device



July 1, 1930.

W. B. HOLLINGSHEAD.

' --soUND DAMPING DEVICE original med Aug. so. 1919 Patented .lilly l, i939 istat SOUND-DAMFING' DEVICE.

Application filed August 30, 1919, Serial No. 320,786. Renewed March 13, 1929.

This invention has reference to sound boxes for sound-recording and reproducing machines, and the objects of the invention are to provide a device of this character which will record and reproduce the trueV tonal characteristics and at the same time will be of practical and relatively inexpensive construction.

Special features of the invention relate to the control of the sound vibrations so as to gain true reproductions of the original sounds with the full harmonics and over tones. Y

In the accompanying drawing, I have illustrated various embodiments of my invention, but would have it understood that the invention is not limited to these particular disclosures. K

In the drawing referred to, Figure l is a face view of one form of the sound box, the neck of the sound boX and the stylus bar being indicated as broken away; Figure 2 is a vertical sectional View on substantially the plane of line 2-2 of Figure l; Figures 3 25 and l are views similar to the rst two figures of another form of the invention; likewise Figures 5 and 6, and 8, 9 are similar views of two other forms of the invention; Figure 7 is a graphic reproduction of the damping 3o effect obtained with the construction disclosed in Figures 5, 6; VFigure 10 is an enlarged sectional view of a further development of a modification illustrated in'Figure 9; Figure 11 is a face view of another form of the sound box; Figure 12 is a detailed view of a special form of mounting for the stylus bar.

15 designates a sound-box casing which may be of the open construction illustrated in Figures 2, 4 and 9, or may be closed at the back as indicated at 16 in Figure 6. The casing is provided with a suitable neck portion 17 by which it is attached to the sound-vibration-transmitting arm (not shown), and which arm may be of the construction disclosed and claimed in conpending applications of mine. This casing is usually constructed of a heavy and relatively dead material such as lead. 18 designates the diaphragm which may be madel of ironvor steel or other suitable material. 19 designates the stylus bar which may be connected with the central part of the diaphragm in the usual way, but which in a preferred construction is vconnected with the diaphragm as indicated at 2O in Figure 11, that is, near one edge and at a distance anywhere from'the edge substantially equal to one-nintli of the diameter of the diaphragm. `I find that the connection of the stylus at this point does away with certain objectionable elements in tonercproduction and produces superior results, due possibly to ythe Vrelation of this point to the nodal characteristics of the diaphragm. In the iirst formillustrated, a control of the Vvibration effectsis obtained by applying aV sectoral damping-element 2l over the upper sectoral portion of the diaphragm and by providing a cover 22 of greater area over 70 said damper. Thiskcover not only shields and conceals the 'damper but apparently adds a somewhat mellow and improved tone to the apparatus. Y

In vthe form shown in Figures' and 4, 75 two sectoral dampers 23v are applied to the face of the diaphragm at opposite sides of the center thereof, said dampers being substantially in the form of quadrants. These damping elements may be in the form of 50 adhesive fabric or fabric adhesively applied to the diaphragm.

Similarly, in the constructions illustrated in Figures 8, 9 and 10 the damping elements may be in the form of adhesive fabric, said S5 elements consisting in these latter disclosures of a series of plies or superposed discs 24 applied either to one (Figures 8, 9) or both (Figure 10) faces of the diaphragm.

I find that particularly quick results are obtained if the diaphragm is considered as divided into sectors corresponding in number to eight, or multiples of eight, and the corresponding dampers are applied to the sectors insuch relation. In Figures 5 and 95 6 I have indicated a diaphragm as divided into sixteen sectors and have shown altervnate sectors 25, 26 as engaged by damping circumferentially adjustable Within a slot or annular guideway 30 provided in the ring member 31 which is secured to the face of the sound-box casing. By means of this construction the damper may be adjusted circumferentially about the peripheral portion of the diaphragm to bring the damping elements into engagement with any two alternate sectors desired; and this slide can be easily adjusted until the best effect is obtained. This damping effect is indicated graphically in Figure 7 Where alternate sectoral portions 25 and 26 are designated as the crests of Waves 25 and 26 from which it will appear that the dampers 27-28 check the vibrations of these sectors, while leaving the other sectors free to vibrate.

In Figure 12 the stylus bar 32 is shown as looped about the diaphragm and as connected therewith by simple contact at the point 33, the mounting of the bar at 34 exerting suflicient tension to hold the bar properly engaged with the face of the diaphragm.

I claim:

1. A sound-box casing, a diaphragm mounted in said casing, a ring carried by said casing and having an annular slot therein and a vibration-controlling member adjustably engaged in said slot, and engaging the diaphragm.

2. A sound-box Y casing7 a diaphragm mounted in said casing, a ring carried by said casing and having an annular slot therein and a vibration-controlling member adjustably engaged in said slot, and provided with separated projections for engagement with the diaphragm at different spaced portions of the surface thereof.

In testimon whereof I affix my signature.

WILLI M B. HOLLINGSHEAD. 

